Speaking about the 50th special, Moffat told the Radio Times: "It was great fun. You'd have David [Tennant] and Matt [Smith], they'd be leaping around the set and doing every form of physical comedy with each other - and, you know, slightly competing about who could be slightly more insane than the other - and then John Hurt would come along and do this [tiny movement] with his eyes and you go 'That's it - he's got the scene now, hasn't he?'"

The executive producer described 73-year-old Hurt as "delightfully grumpy".

"John was delightful - delightfully grumpy in every single way," he explained. "During our last meal [while filming] he got grumpy about the fact that he liked the wine!